sedimentary

Agate

Silicon dioxide (Chalcedony), SiO2

Hardness of 6.5 to 7 on the Mohs scale, waxy luster, microcrystalline structure, and displays distinct concentric color banding.

Identified October 26, 2026More sedimentary →

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Physical properties

Hardness of 6.5 to 7 on the Mohs scale, waxy luster, microcrystalline structure, and displays distinct concentric color banding.

Formed by the deposition of silica from groundwater in cavities of igneous and sedimentary rocks over millions of years.

Widely used for making decorative objects, jewelry, ornaments, and precision instruments.

Agate is one of the most common materials used in the ancient art of lapidary and stone carving.

Easily identified by its characteristic curved banding and waxy luster; commonly found worldwide in volcanic rock cavities.

Fossil-bearing concretion, possibly containing a fossil shell or other organic inclusion

Calcareous concretion; exact fossil and host-rock composition are not identifiable from the image

Fossiliferous Sedimentary Rock

Sedimentary limestone with invertebrate fossil imprint

Sandstone or Siltstone

Arenite (if sandstone)

Sandstone

Arenite

Shale

Shale (clastic sedimentary rock)

Shale (or Mudstone/Siltstone)

Sedimentary Mudrock (SiO2, Al2O3 base with clay minerals)